1. Field of the Invention
The present invention relates to a semiconductor device and manufacturing method thereof. More particularly, the present invention relates to a non-volatile memory and manufacturing method thereof.
2. Description of the Related Art
Electrically erasable programmable read only memory (EEPROM) is a type of non-volatile memory that allows multiple data writing, reading and erasing operations. Furthermore, the stored data will be retained even after power to the device is removed. With these advantages, EEPROM has been broadly applied in personal computer and electronic equipment.
A typical EEPROM has a floating gate and a control gate fabricated using doped polysilicon. To prevent data errors due to the over-erasure of EEPROM during an erase operation, an additional select gate is often set up on the sidewalls of the control gate and the floating gate and the upper surface of the substrate to form a split-gate structure.
Because some areas must be reserve to set up the split gate structure, each memory cell has a standard size greater than the stacked gate structure. Thus, increasing the level of integration of memory devices is difficult.
Furthermore, each memory cell in the split gate memory can only hold a single bit of data. With an ever-increasing size of software application programs, the demand for memory storage areas is constantly increasing. Since the conventional split-gate memory structure can hardly be miniaturized any further, the structure and/or the manufacturing method must be modified so that deep sub-micron memory devices having a larger memory storage capacity can be produced.